As it is the first Breathing Blog post, it’s only fitting that we start at the beginning. We are almost never exempt from the environment we live in. We hear the sounds, we smell the scents, see the sights and we breathe the air. A fetus in a pregnant woman is not exempt from the impact of the environment on one’s health. In fact, exposures during the critical period of lung development in utero (gestation) can leave lasting effects on the future respiratory health of your child.

Prenatal Impact:

Lung development begins within the first month or two of gestation and believe it or not, air pollution can impact lung development quite substantially. Over the next few months of the pregnancy, a baby’s lungs begin branching, elongating and maturing. Pollution that you inhale can actually impair some of this development. Often this is challenging to identify at birth or even early on in infancy, but these exposures have been associated with the later diagnoses of asthma and allergies. In fact, there is an increased incidence of asthma in children born to non-smoking mothers whose grandmothers were smokers. While it’s generally understood that tobacco smoking, second hand smoke exposure and even third hand smoke exposure is detrimental to lung development, there is evolving evidence that other pollutants impact lung development as well.(1) 20% of children born to mothers exposed to the Great Smog of London in 1952 went on to develop asthma and another 10% developed asthma later in adult life.(2) Burning fossil fuels such as oils or gasoline produce particulates such as PM10 (particulate matter less than 10 ng in size) and PM2.5 (less than 2.5 ng in size), as well as NO2, benzene, polycyclic aromatic hydrocarbons (PAH) and CO all of which have been linked to impaired lung function when exposed in utero.(1,2)

Impact During Infancy and Childhood:

After birth, the lungs continue to grow and develop well into our teenage years and probably into our mid 20’s. Our lungs begin to inhale our environment as soon as we’re born as air is ubiquitous and impossible to avoid. Any pollutants inhaled have to face a number of protective mechanisms in our airways, but these are not perfect, and can easily be overwhelmed. Particles with a larger size, such as PM10, land in our larger airways and cam get caught in our airway’s muco-ciliary escalator (little hair like projections lining our airways that move mucous and debris up the airway). The body also has an air-blood barrier that can act as a filter to prevent absorption of pollutants. Further, we have white blood cells, called macrophages, in our lungs that help to digest larger particulates. Unfortunately, these defense mechanisms are easily overwhelmed and consequences of exposure to pollution can occur.

Increased Risk for Respiratory Infections:

Exposure to air pollution increases the risk of acquiring respiratory infections, often these are more severe than in non exposed persons with similar infections. This is quite common in larger cities where a high NO2 and particulate matter (PM2.5 and PM10) burden were associated with an increased amount of influenza and other viral respiratory tract infections.(3)

Increased Airway Inflammation:

Ozone, diesel exhausts, PM10, polyurethane foam (building insulation, electronics, bedding, surf boards etc.), toluene diisocyanide (used in making polyurethane foam) up-regulate several types of white blood cell activity within the lungs increasing the propensity for airway inflammation and chronic cough.(4)

Increased Risk for Developing Asthma and Allergies:

Similar to pre-natal exposures, post-natal exposure to pollutants has been associated with the development of chronic respiratory conditions such as asthma, allergies or chronic cough. Notable pollutants that increase sensitization to aeroallergens (such as dust, pollen or cockroaches) include NO2, diesel exhausts and PAH and unfortunately, an increased sensitivity to aeroallergens increases the risk of developing asthma.(5)

Asthma and Allergy Exacerbations:

Not only do children exposed to high levels of pollution have an increased risk of developing asthma, but ozone (O3), CO, NO2, SO2, PM10, PM2.5, dust mite, pollen, pet dander and smoke can all exacerbate asthma and cause a more severe allergic response.(6) (7) (8)

Air pollution is a significant problem that all of us are challenged with increasing the risk of abnormal lung development and worsening respiratory conditions such as asthma and allergies. These challenges begin early and really persist throughout life if exposures continue. It is imperative that we seek ways to reduce exposure to our most vulnerable population, our infants and children.

References

Air pollution during pregnancy and lung development in the child. Insa Korten, Kathryn Ramsey, Philipp Latzin. 2017, Pediatric Respiratory Reviews, Vol. 21, pp. 38-46.
A retrospective assessment of mortality from the London Smog Episode of 1952: The role of influenza and pollution. Michelle L. Bell, Devra L. Davis and Tony Fletcher. 2004, Vol. 112, pp. 6-8.
Air pollution and acute respiratory infections among children 0-4 years of age: an 18-year time-series study. Darrow LA, Llein M, Flanders WD, Mulholland JA, Tolbert PE, Strickland MJ. 2014, American Journal of Epidemiology, Vol. 180, pp. 968-970.
Air pollutants and early origins of respiratory diseases. Dasom Kim, Zi Chen, Lin-Fu Zhou, and Shou-Xiong Huang. 2018, Chronic Diseases and Translational Medicine, Vol. 4, pp. 75-94.
Environmental determinants of allergy and asthma in early life. Allison J Burbank, Amika K Sood, Matthew J Kesic, David B Peden and Michelle L Hernandez. 1, 2017, Journal of Allergy and Clinical Immunology, Vol. 140, pp. 1-12.
Impact of air pollution on the burden of chronic respiratory disease in China: time for urgent action. Wei-Jie Guan, Xue-Yan Zheng, Kian Fan Chung, and Nan-Shan Zhong. 2018, Lancet, Vol. 4, pp. 75-94.
The dangerous liaison between pollens and pollution in respiratory allergy. Schiavoni G, D'Amato G, Afferni C. 2017, Annals of Allergy, Asthma and Immunology, Vol. 118, pp. 269-275.
Pulmonary health effects of air pollution. Kurt OK, Zhang J, and Pinkerton KE. 2016, Current Opinions in Pulmonary Medicine, Vol. 22, pp. 138-143.